1. Field of Invention
This invention relates to containers and, more particularly, to food containers which are made from molded plastic and used for take-out food.
2. Art Relating to Invention
Plastic food containers typically have a base with tall side walls and a lid with short side walls. The two mate along their respective rims to form a seal. They are made in a simple molding process from plastic and, although reusable by the customer, are not returned to the restaurant.
These containers must be reusable, or resealable so that leftovers can be stored in the same container. The seal must be flexible enough to allow for fairly easy opening and closing, yet tight enough to provide a secure seal against either leakage of food from the container or introduction of air and microbes into the container to prevent spoiling. Thus, there is a balance between providing a strong solid seal and a removable seal.
Also, it is important that the container have a rim that extends out from the body of the container to allow the user to hold the container without burning his hands on the hot food. Since the containers are made of thin plastic, the body of the container provides little or no insulation between the hands of the user and the hot food inside the container. Thus, the rim of the container must be wide enough and strong enough to be grasped by the user and support the food-ladened container.
It is also important that the containers be stackable, one on top of the other.
The art relating to plastic, molded food containers with resealable lids is plentiful, see for example, U.S. Pat. Nos. 6,056,138; 5,833,116; 5,758,791; 5,395,003; 5,377,860; 5,356,026; 4,844,263; 4,555,043; 4,360,118; 4,042,143; 3,861,433; and 2,798,631. Each of these references have different sealing arrangements between the lid and the base.
A unique sealing arrangement has now been discovered for use with a plastic molded food container. Specifically, a plastic molded food container with four seals has been found to provide a good, secure sealing arrangement to prevent leakage of food and to prevent spoilage from air and microbes while still providing for easy removal of the lid and resealing of the lid. The four seals include an exterior seal, two middle seals and an interior seal, where one of the middle seals has a surface area equal to or greater than any of the other three seals. Additionally, by making this large middle seal in a horizontal orientation, the rim of the container extends out enough to allow the user to hold the container without burning fingers.
Broadly, the plastic molded food container of the present invention can be characterized as comprising
(A) a base having
(i) a substantially planar bottom;
(ii) base side walls extending substantially vertically upward from said bottom;
(iii) a base flange extending substantially horizontally outward from said base side walls;
(iv) an inverted, U-shaped base rim extending outward from said base flange, said base rim having
(a) an inner base rim surface which extends substantially vertically upward from said base flange;
(b) a middle base rim surface which extends substantially horizontally outward from inner base rim surface;
(c) an exterior base rim surface which extends substantially vertically downward from said middle base rim surface;
(B) a lid having
(i) a substantially planar top;
(ii) lid side walls extending substantially vertically downward from said top;
(iii) a lid flange extending substantially horizontally outward from said lid side walls;
(iv) an inverted, U-shaped lid rim extending outward from said lid flange and mating with said inverted, U-shaped base rim when said lid is locked onto said base, said lid rim having
(a) an inner lid rim surface which extends substantially vertically upward from said lid flange;
(b) a middle lid rim surface which extends substantially horizontally outward from said inner lid rim surface;
(c) an exterior lid rim surface which extends substantially vertically downward from said middle lid rim surface;
(C) a locking lip which extends vertically downward from said exterior lid rim surface and locks said lid onto said base;
(D) four seals which form when said lid is locked onto said base, said four seals being
(i) a horizontal inner seal formed by said lid flange and said base flange;
(ii) a vertical middle seal formed by said inner base rim surface and said inner lid rim surface;
(iii) a horizontal middle seal formed by said middle base rim surface and said middle lid rim surface;
(iv) a vertical exterior seal formed by said exterior base rim surface and said exterior lid rim surface;
(E) two air pockets formed between said four seals, a first air pocket formed between said horizontal inner seal and said vertical middle seal, and a second air pocket formed between said vertical middle seal and said horizontal middle seal; and
(F) said horizontal middle seal having a surface area equal to or greater than said horizontal inner seal, said vertical middle seal, and said vertical exterior seal.
Preferably, the horizontal middle seal is greater than said horizontal inner seal, said vertical middle seal, and said vertical exterior seal, taken individually.
In order to provide a good seal, it is preferred that said horizontal middle seal and said vertical exterior seal are continuous, in other words, the corner between these two flat seals is also a seal.
In order to make the food container of the present invention stackable, the plastic food container of the present invention can be further characterized as the lid further comprising a raised central portion on said planar top and said base further comprises a raised central portion on said planar bottom which is matable with said raised central portion of said planar top when one container is stacked on another container.